Immune responses induced by vaccination can be categorized broadly into humoral or cellular types. A humoral response is typically desired to protect against viral or bacterial invaders, whereas immunity against virally infected cells and cancer cells typically involves a cell mediated response. Humoral immunity is typified by high levels of antibody production by B cells, whereas cellular immunity is characterized by increased activation of cytotoxic CD8+ T lymphocytes.
Many vaccines that have shown promise in pre-clinical development have ultimately failed to demonstrate clinical benefit when tested in humans. As relates to cancer vaccines, therapeutic intervention is a complex challenge, and many aspects of the disease such as timing of therapy relative to standard of care, stage and type of cancer all have influence on the outcome of treatment. However, there are three features of immunotherapy that may provide better outcome if they are stringently combined: (1) vaccine immunogenicity (i.e. adjuvant); (2) appropriate selection of tumor associated antigens; and (3) ability to overcome tumor induced immune suppression (Weir et al., Cancer 3: 3114-3142, 2011; Berzofsky et al., Semin Oncol 39(3): 348-357, 2012).